This invention relates generally to a diagnostic tool for evaluating a patient""s oculomotor system, and more particularly for determining whether the patient""s oculomotor system is in balance or not.
When a person looks at a particular object, there are two major systems that the person""s body utilizes in order to ensure that the object is accurately viewed. One of the systems is the accommodative system, which is the system that changes the shape of the lenses in the eyeballs to make sure the images are properly focused on the person""s retinas. The other system is the vergence system, which is the system responsible for moving the eyeballs so that they are properly aimed at the object being looked at. Both systems provide a source of innervation, i.e. nerve stimulation, to the oculomotor system. The innervation stimulates the muscles of the eyes in order to change their alignment and focusing so that an object can be viewed correctly. Both the accommodative (focusing) and vergence (aiming) systems can, within certain limits, correct for imperfections in the other system. There is, however, a normal range of innervation that each system comfortably supplies, and when either one of these systems moves outside that normal range, the patient experiences oculomotor dysfunction, or imbalance.
For most conventional eye examinations, there are usually a limited number of standard visual diagnostic tests that are performed. Because of the time-consuming nature of evaluating whether a patient has oculomotor dysfunction, such tests are often not part of the ophthalmic practitioner""s standard eye examination. When not diagnosed and treated, however, oculomotor dysfunction can have many adverse effects for the patient, including reading discomfort, burning sensations, sleepiness, or even diplopia, among others. A need therefore exists for a simple diagnostic tool capable of evaluating whether a patient""s oculomotor system is in balance or not.
Accordingly, the present invention provides a simple, efficient diagnostic tool for determining whether a patient""s accommodative and vergence systems are in balance or not. According to one aspect of the present invention, a diagnostic tool is provided that includes a first test for measuring a patient""s heterophoria and a second test for measuring a patient""s fixation disparity. The tool further includes an instrument for determining whether the measured heterophoria and fixation disparity indicate that the patient""s accommodative and vergence systems are in balance or not.
According to another aspect of the present invention, a diagnostic tool is provided that includes a base with a front surface. A test for heterophoria and a test for fixation disparity are both positioned on the front surface of the base. An instrument is provided for determining if the patient""s measured heterophoria and fixation disparity indicate that the patient""s accommodative and vergence systems are in balance or not.
According to still another aspect of the present invention, a method is provided for determining a patient""s oculomotor imbalance. The method includes measuring the patient""s heterophoria and fixation disparity, and then determining whether the measured amount of the patient""s fixation disparity is normal for the measured amount of heterophoria. If it is not, then it is concluded that the patient""s oculomotor system is out of balance.
According to still other aspects of the present invention, the tests for heterophoria and fixation disparity may be mounted on a near-point card. The instrument for determining whether the measured amount of fixation disparity is normal or not for a given amount of heterophoria may include a graph printed on the card indicating the normal relationship for fixation disparity and heterophoria. The heterophoria test may be a modified Thorington test. The fixation disparity test may include a plurality of areas containing first and second images that are each positioned behind oppositely polarized materials. By determining when the images appear aligned to the patient, the fixation disparity can be measured. The card may also include additional diagnostic tests for helping to pinpoint the oculomotor imbalance, should such an imbalance be detected.
The present invention provides a quick, cost-effective, and efficient way for determining whether a patient""s oculomotor system is in balance or not. Because the invention can be performed so easily, it readily can be implemented into standard eye-examinations, thereby allowing proper treatment to be given to those individuals suffering from oculomotor dysfunction. These and other advantages of the present invention will be apparent to one skilled in the art in light of the following specification when read in conjunction with the accompanying drawings.